Load balancing of integrated ITS

[Former Member]

Hello!

I need to set up load balancing for integrated ITS. We are using several instances - each instace have it's own WAS and ICM.

For load balancing there should be installed SAP Web Dispatcher. Where should it be installed?

I have questions according parameters of SAP Web Dispatcher. There could be maintained such parameters for SAP Web Dispatcher:

1. Description of the Access Points

icm/server_port_0 = PROT=HTTP,PORT=80

icm/server_port_1 = PROT=ROUTER,PORT=443

1. Description of the Resources

icm/min_threads = 20

icm/max_threads = 40

icm/max_conn = 500

Since ICM uses the same parameters - then there appears a question where to maintain parameters for SAP Web Dipatcher. Should I set those parameters for central instance or does it have its own parameters?

If those parameters are set on central instance or some own profile - how they are related to other instances? For example, if I have 5 instaces. Does upper parameter (icm/max_conn = 500) limits connections to 100 per instance? Or this parameter is a central place for all other instances, which means that each instance has limit of 500? If the second is true - should I set this parameter in all instances the same or I just can skip it because it would be taken from central instace by default?

Best regards,

Rorijs

[Former Member · Accepted solution]

Hi ,

As per my knowledge you can install it anywhere either in CI or in a new host beacuse this is nothing but a service which runs with parameters given by us.

During installation we give all the information of instances to be configured with Webdispatcher .You can get more information in SAP Note 538405 - Composite SAP Note: SAP Web Dispatcher and Note 928952 - Web Dispatcher Installation based on NW 7.0(2004s).

Thanks..

Mohit

[Former Member · Accepted solution]

Hi Mohit,

Thank you for the answer!

But how about those icm/... parameters which restricts the connection on Web Dispatcher? If Web Dispatcher can be installed on a separate server then I assume that it has its own parameters, which are not connected to some of ICMs of existing instances - am I right?

If Web Dispatcher has its own parameters - does they have the same limitations as ICM parameters? And does parameter "icm/max_conn = 500" is the total sum of "icm/max_conn" values for each instace (ICM)?

Best regards,

Rorijs

[cris_hansen · Accepted solution]

Hello Rorijs,

The SAP Web Dispatcher actually is built using the ICM; this is the reason why the parameters are the same (and so eventual limitations).

I hope this might help.

All the best,

Cristiano

[Former Member]

Hi,

WebDispatcherICM Ports

If you install the WebDispatcher on your central instance and the ICM on your CI is setup to use port 80(http) and 443(https)

you might want to change these ports in the CI's instance profile, port 81 & 444 e.g. If you don't there will be a conflict between which application that shall use the ports.

Configuration of connections

Independent of type of loadbalancing you have chosen (regularweighted) I would recommend that you increase the 'max connection' parameter on the dialog instancesapplication servers with 50%, eg. to 150 connections maby.

If one of the instances should "fall out", for any reason, you would still have the capacity to take the load from the WebDispatcher on the other instances.

If you set the parameter in the default profile instead of instance profile all of the instances will "read" the same parameter.

Kind Regards

Håvard Fjukstad.

[Former Member]

Hello folks,

Since we have installed Web Dispatcher and running it on our Productive system then now I'm more informed about this system.

I would like to update this thread in case anyone else wants to find out those questions:

1. Web Dispatcher is a separate service which is installed just like any other SAP instance (it even have it's own instance).

2. It has it's own ICM parameters which are managed in the Web Dispatcher's profile file: sapwebdisp.pfl

3. Answer to the question that noone has answered me: Parameters of the Web Dispatcher influences the systems behind, i.e., if you have set icm/max_conn = 500 for the Web Dispatcher and you have 5 instances to load balance to, then there is no use of setting more that 100 for the parameter icm/max_conn of ICM of each instance. This information is observed in our system (max connections used in Web dispatcher (administraion) is aprox. SUM of max connections of all WAS (tr. SMICM)).

That means - if you are using full capacity of Web Dispatcher - you cannot add one more server to handle more requests. So for my observersions seems that each parameter of Web Dispatcher (connections, work threads, MPI memory etc.) should be greater or equal to the SUM of all servers to load balance.

But the best part of it is that active connections are not equal to active sessions. Each active session (dialog step) will create several connections - but active session does not mean active connections, i.e., after connection is established MPI memory is released and after icm/keep_alive_timeout (Web Dispatcher) these connections are discarded to free up the slots for the new connections. So in our reality - we have more active sessions than active connections although each dialog step of user can open several connections (as stated in the Note 538405).

So at the moment we are very far from the limits of the Web Dispatcher. And This means that the thinktime_per_diastep_sec of the estimation formula in our case is much larger than any examples in notes and documentations shows:

concurrent_conn = (users * req_per_dialog_step * conn_keepalive_sec)/ (thinktime_per_diastep_sec)

If you have some objections or correction - feel free to comment! But I'm closing this thread!

Best regards,

Rorijs

[Former Member]

Hello!

Have anyone used the load balancing of message server for services of integrated ITS? I have found the note 1040325 and some more information that using a message server you can face some disadvantages, for example, that several IP addresses

must be known, authentication is required after changing the application server.

What does it means "authentication is required after changing the application server" for integrated ITS? If user opens several Web transactions each of request can be processed to other WAS and this forces user to enter logon data again, is that so?

Best regards,

Rorijs

P.S. Questions in the previous messages are still open, too.

[cris_hansen]

Hello Rorijs,

SAP always recommend to use the Web Dispatcher for load balancing.

Please also have a look at SAP note 1055324 (POST parameters lost during redirect) if you intend to use the message server for load balancing.

Could you please clarify from where you have found "authentication is required after changing the application server"?

I hope this helps.

Regards,

Cristiano

[Former Member]

Hello Cristiano,

Thank you for the update!

Such problems of authentification is mentioned in the document "SAP Web Application Server in Switchover Environments".

OK! I know the upper limits of SAP Web Dispatcher, which are the same as for ICM (and your answer clearifies why it's so), but it does not help to answer question - how the parameter, which is set in Web Dispatcher, limits the same parameter of each ICM (the WAS to which I'm load balancing)? Can you help me to clarify this?

Best regards,

Rorijs

[cris_hansen]

Hello Rorijs,

The Web Dispatcher is an independent software; it doesn't influence the parameters of your application server.

Cheers,

Cristiano

[Former Member]

Hello Cristiano,

Probably I have not stated my question correctly. I know that Web Dispatcher is separate system with it's own parameters. But that is a thing about what I'm not sure - that those parameters does not limit parameters of each instance behind. It's not like technical limitation of value, i.e. if I set icm/max_conn = 500 for Web Dispatcher - I'm still able to set icm/max_conn = 16350 for each instance.

But the question is: what is the reasonable value for each instance if I'm looking from the values of Web Dispatcher?

If I had 5 equal instances for load balancing and icm/max_conn = 500 for Web Dispatcher - what would be the reasonable value for each instance? And why?

By the light of nature seems that there is no use of setting more than icm/max_conn = 100 for each of 5 instances behind.

Best regards,

Rorijs